The present invention relates generally to containers for material handling, shipping and storing rigid, planar objects, and which may also be used as a production and in the manufacture of such objects. More particularly, the present invention is directed to an improved electrically conductive container for grounding circuit boards and the like having static sensitive devices on such planar objects, such as for example devices which have metal oxide semi-conductors.
Containers for circuit boards or other objects having static sensitive devices are known in the art. For example, in one arrangement, a container box is employed which is formed completely of conductive plastic material so that the entire container is conductive. In this arrangement, the container is molded entirely from plastic material and is provided with outer side walls and interior walls which together define a plurality of individual compartments for loosely receiving static sensitive devices as well as other types of devices, and for storing or housing same during non-use. However, because the devices to be stored are only loosely received in the compartments (i.e., they are not positively held in place), it is possible that the devices might pick up a static charge, the discharge of which might damage or possibly destroy the device entirely, such as by a blow-out or the like. Furthermore, although such containers may in some instances be satisfactory in minimizing the chances of static build up, the containers are relatively quite expensive to manufacture, since the entire container must be formed of conductive plastic material and since the entire container is molded.
In another prior art arrangement, a cardboard container is employed, and is provided on its interior walls with anti-static plastic members. This anti-static plastic members are slotted with ribs for receiving the static sensitive devices. However, the problem with such arrangements is that they are not electrically conductive but are merely anti-static. This difference is significant, since it has been found that anti-static members cannot not always be relied on to be electrically conductive, especially on dry days, since the anti-static members appear to require moisture in order to operate to some extent and be conductive so as to prevent static build up.
In a still further arrangement of the prior art, a cardboard shipping container or box is employed which is provided with an electrically conductive coating sprayed on the entire interior of the box. Such containers are mainly used for shipping of printed circuit boards and the like by wrapping the printed circuit boards in a static free plastic cushioning, and then inserting the packaged circuit board into the box. In some instances, the containers may include suitable conductive partitions therein for use in shipping a plurality of printed circuit boards. Again, however, even with the multiple partitioning type of arrangement, no means are provided for positively holding and retaining in place the circuit boards having static sensitive devices thereon and for ensuring suitable grounding of the devices with respect to their environment since there is no assurance that the circuit boards and the static sensitive devices are in contact with the electrically conductive coating on the interior of the box and since no means are provided for grounding the interior of the box with respect to its environment. This is particularly true when the printed circuit board is wrapped with a static-free cushioning material.
Accordingly, it is highly desirable to provide an arrangement which is capable of positively receiving and holding rigid planar objects, in particular objects having static sensitive devices, in a manner to ensure against, or at least minimize the possibly of static build up while at the same time accomplishing such purpose in a relatively inexpensive manner. In this regard, it is also highly desirable to provide a container which is electrically conductive at all times, and further, is less costly to manufacture as compared to containers which are entirely electrically conductive as described above. Still further, it is desirable to provide a container which positively holds and receives rigid planar objects having static sensitive devices thereon, and which also provides a simple, efficient and inexpensive manner of grounding of the container and circuit boards and the like which contain static sensitive devices.